The present invention relates to a disc drive micro-actuator, and more particularly to a sealed micro-actuator which provides a contaminant free environment for proper operation.
The density of concentric data tracks on magnetic discs continues to increase (that is, the width of data tracks and radial spacing between data tracks are decreasing), requiring more precise radial positioning of the head. Conventionally, head positioning is accomplished by operating an actuator arm with a large-scale actuation motor, such as a voice coil motor, to radially position a head on a flexure at. the end of the actuator arm. The large-scale motor lacks sufficient resolution to effectively accommodate high track-density discs. Thus, a high resolution head positioning mechanism, or micro-actuator, is necessary to accommodate the more densely spaced tracks.
Electro-static micro-actuators rely on a contaminant free environment to function properly. The large electro-static charge required to actuate the combs or electrodes of a micro-actuator can attract debris. The debris can cause a short and a failure of the device.
Certain mechanical micro-actuator devices, such as accelerometers, that do not have to interact mechanically with the outside world are easy to seal up. The device is put in a cavity and sealed therein. However, micro-actuator devices such as those used in a disc drive head must interact with the outside world and cannot be completely packaged within a cavity.
Currently, no satisfactory solutions exist for sealing disc drive micro-actuator devices. One method that has been proposed for sealing a micro-electro-mechanical system (MEMS) involves wafer bonding of the MEMS device after it has been fabricated. During wafer to wafer bonding, cavities are etched in a first wafer that correspond to areas that are to be encapsulated in a second wafer. The first wafer is then bonded across-the top of the second wafer. For wafer to wafer bonding to work, the wafers have to be very smooth and flat at the atomic level. In the long range, the wafers have to be flat, and in the short range, the wafers have to be smooth (i.e., within about an angstrom of roughness), or the wafers will not properly bond. In addition, metal lines are occasionally put down on the surface of MEMS devices which makes it very difficult to obtain the necessary flatness for wafer to wafer bonding. Therefore, wafer to wafer bonding does not present a satisfactory solution for sealing disc drive micro-actuator devices.
A sealed micro-actuator device for positioning a slider in a disc drive comprises a micro-actuator body, which includes a stator, a rotor, and a motor for moving the rotor with respect to the stator. The micro-actuator device includes means for sealing the micro-actuator body to prevent debris from reaching the motor. In a preferred embodiment, the means for sealing comprises a plurality of cavities formed in the micro-actuator body and an injection molded polymer seal with a plurality of protrusions that extend into the plurality of cavities. A first subset of the plurality of protrusions make contact with the stator, thereby holding the means for sealing in place. A second subset of the plurality of protrusions extend into cavities formed in the rotor. The second subset of protrusions does not contact the rotor.
In an alternative preferred embodiment, a first and a second surface of the rotor are recessed from a first and a second surface of the stator, and the means for sealing comprises a first flexible film heat sealed to the first surface of the stator and a second flexible film heat sealed to the second surface of the stator.
In another alternative embodiment, a sealed actuator is incorporated into a slider of a disc drive. The slider comprises a slider body, a data transfer element, and an actuator. The data transfer element transfers data to or from a magnetic medium. The actuator is coupled between the slider body and the data transfer element. The actuator is operable to move the data transfer element relative to the slider body. The slider includes sealing means to prevent debris from reaching the actuator.